Tropical cyclone forecasting is the science of forecasting where a tropical cyclone's center, and its effects, are expected to be at some point in the future. There are several elements to tropical cyclone forecasting: track forecasting, intensity forecasting, rainfall forecasting, storm surge, tornado, and seasonal forecasting. While skill is increasing in regard to track forecasting, intensity forecasting skill remains nearly unchanged over the past several years. Seasonal forecasting began in the 1980s in the Atlantic basin and has spread into other basins in the years since.

The methods through which tropical cyclones are forecast have changed with the passage of time, the first known forecasts in the Western Hemisphere were made by Lt. Col. William Reed of the Corps of Royal Engineers at Barbados in 1847. Reed mostly utilized barometric pressure measurements as the basis of his forecasts. Benito Vines introduced a forecast and warning system based on cloud cover changes in Havana during the 1870s, before the early 1900s, though, most forecasts were done by direct observations at weather stations, which were then relayed to forecast centers via telegraph. It wasn’t until the advent of radio in the early twentieth century that observations from ships at sea were available to forecasters, the 1930s saw the usage of radiosondes in tropical cyclone forecasting. The next decade saw the advent of aircraft-based reconnaissance by the military, starting with the first dedicated flight into a hurricane in 1943, and the establishment of the Hurricane Hunters in 1944; in the 1950s, coastal weather radars began to be used in the United States, and research reconnaissance flights by the precursor of the Hurricane Research Division began in 1954.[1]

The launch of the first weather satellite, TIROS-I, in 1960, introduced new forecasting techniques that remain important to tropical cyclone forecasting to the present; in the 1970s, buoys were introduced to improve the resolution of surface measurements, which until that point, were not available at all over sea surfaces.[1]

In the late 1970s, William Gray noticed a trend of low hurricane activity in the North Atlantic basin during El Niño years. He was the first researcher to make a connection between such events and positive results led him to pursue further research, he found numerous factors across the globe influence tropical cyclone activity, such as connecting wet periods over the African Sahel to an increase in major hurricanelandfalls along the United States East Coast. However, his findings also showed inconsistencies when only looking at a single factor as a primary influence.[2]

Utilizing his findings, Gray developed an objective, statistical forecast for seasonal hurricane activity; he predicted only the number of tropical storms, hurricanes, and major hurricanes, foregoing specifics on tracks and potential landfalls due to the aforementioned inconsistencies.[2] Gray issued his first seasonal forecast ahead of the 1984 season, which used the statistical relationships between tropical cyclone activity, the El Niño–Southern Oscillation (ENSO), Quasi-biennial oscillation (QBO), and Caribbean basin sea-level pressures,[3][4] the endeavor proved modestly successful.[2] He subsequently issued forecasts ahead of the start of the Atlantic hurricane season in May and before the peak of the season in August.[5] Students and colleagues joined his forecast team in the following years, including Christopher Landsea, Paul W. Mielke Jr., and Kenneth J. Berry.[6]

The large-scale synoptic flow determines 70 to 90 percent of a tropical cyclone's motion, the deep-layer mean flow is considered to be the best tool in determining track direction and speed. If storms are significantly sheared, use of a lower-level wind is a better predictor. Knowledge of the beta effect can be used to steer a tropical cyclone, since it leads to a more northwest heading for tropical cyclones in the Northern Hemisphere, it is also best to smooth out short term wobbles of the storm center in order to determine a more accurate trajectory.[7]

Because of the forces that affect tropical cyclone tracks, accurate track predictions depend on determining the position and strength of high- and low-pressure areas, and predicting how those areas will change during the life of a tropical system. Combining forecast models with increased understanding of the forces that act on tropical cyclones, and a wealth of data from Earth-orbiting satellites and other sensors, scientists have increased the accuracy of track forecasts over recent decades.[8] An accurate track forecast is important, because if the track forecast is incorrect, forecasts for intensity, rainfall, storm surge, and tornado threat will also be incorrect.

The 1-2-3 rule (mariner's 1-2-3 rule or danger area) is a guideline commonly taught to mariners for severe storm (specifically hurricane and tropical storm) tracking and prediction. It refers to the rounded long-term NHC/TPC forecast errors of 100-200-300 nautical miles at 24-48-72 hours, respectively. These numbers were close to the 10-year average for the 1982–1991 time frame.[9] However, these errors have decreased to near 50-100-150 as NHC forecasters become more accurate, the "danger area" to be avoided is constructed by expanding the forecast path by a radius equal to the respective hundreds of miles plus the forecast wind radii (size of the storm at those hours).[10]

Forecasters say they are less skillful at predicting the intensity of tropical cyclones than cyclone track,[11] they attribute the lack of improvement in intensity forecasting to the complexity of tropical systems and an incomplete understanding of factors that affect their development.

An accurate track forecast is essential to creating accurate intensity forecasts, particularly in an area with large islands such as the western north Pacific and the Caribbean Sea, as proximity to land is an inhibiting factor to developing tropical cyclones. A strong hurricane/typhoon/cyclone can weaken if an outer eye wall forms (typically around 80–160 kilometers (50–100 miles) from the center of the storm), choking off the convection within the inner eye wall. Such weakening is called an eyewall replacement cycle, and is usually temporary.[12]

Dr. Kerry Emanuel created a mathematical model around 1988, called the maximum potential intensity or MPI, to compute the upper limit of tropical cyclone intensity based on sea surface temperature and atmospheric profiles from the latest global model runs. Maps created from this equation show values of the maximum achievable intensity due to the thermodynamics of the atmosphere at the time of the last model run (either 0000 or 1200 UTC). However, MPI does not take vertical wind shear into account.[13] MPI is computed using the following formula:

V=A+B⋅eC(T−T0){\displaystyle V=A+B\cdot e^{C(T-T_{0})}}

Where V{\displaystyle V} is the maximum potential velocity in meters per second; T{\displaystyle T} is the sea surface temperature underneath the center of the tropical cyclone, T0{\displaystyle T_{0}} is a reference temperature (30˚C) and A{\displaystyle A}, B{\displaystyle B} and C{\displaystyle C} are curve-fit constants. When A=28.2{\displaystyle A=28.2}, B=55.8{\displaystyle B=55.8}, and C=0.1813{\displaystyle C=0.1813}, the graph generated by this function corresponds to the 99th percentile of empirical tropical cyclone intensity data.[14]

Tropical cyclone rainfall forecasting is important, since between 1970–2004, inland flooding from tropical cyclones caused a majority of the fatalities from tropical cyclones in the United States.[15][16] While flooding is common to tropical cyclones near a landmass, there are a few factors which lead to excessive rainfall from tropical cyclones. Slow motion, as was seen during Hurricane Danny and Hurricane Wilma, can lead to high amounts, the presence of topography near the coast, as is the case across much of Mexico, Haiti, the Dominican Republic, much of Central America, Madagascar, Réunion, China, and Japan acts to magnify amounts due to upslope flow into the mountains. Strong upper level forcing from a trough moving through the Westerlies, as was the case during Hurricane Floyd, can lead to high amounts even from systems moving at an average forward motion. A combination of two of these factors could be especially crippling, as was seen during Hurricane Mitch in Central America.[17] Therefore, an accurate track forecast is essential in order to produce an accurate tropical cyclone rainfall forecast.[18] However, as a result of global warming, the heat that has built up on the ocean's surface has allowed storms and hurricanes to capture more water vapour and, given the increased temperatures in the atmosphere also, retain the moisture for a longer capacity.[19]This results in incredible amounts of rainfall upon striking land which can often be the most damaging aspect of a hurricane.

Historically, tropical cyclone tracking charts were used to include the past track and prepare future forecasts at Regional Specialized Meteorological Centers and Tropical Cyclone Warning Centers, the need for a more modernized method for forecasting tropical cyclones had become apparent to operational weather forecasters by the mid-1980s. At that time the United States Department of Defense was using paper maps, acetate, grease pencils, and disparate computer programs to forecast tropical cyclones.[20] The Automated Tropical Cyclone Forecasting System (ATCF) software was developed by the Naval Research Laboratory for the Joint Typhoon Warning Center (JTWC) beginning in 1986,[21] and used since 1988. During 1990 the system was adapted by the National Hurricane Center (NHC) for use at the NHC, National Centers for Environmental Prediction and the Central Pacific Hurricane Center.[21][22] This provided the NHC with a multitasking software environment which allowed them to improve efficiency and cut the time required to make a forecast by 25% or 1 hour.[22] ATCF was originally developed for use within DOS, before later being adapted to Unix and Linux.[21]

The main storm surge forecast model in the Atlantic basin is SLOSH, which stands for Sea, Lake, Overland, Surge from Hurricanes.[23] It uses the size of a storm, its intensity, its forward motion, and the topography of the coastal plain to estimate the depth of a storm surge at any individual grid point across the United States. An accurate forecast track is required in order to produce accurate storm surge forecasts. However, if the landfall point is uncertain, a maximum envelope of water (MEOW) map can be generated based on the direction of approach. If the forecast track itself is also uncertain, a maximum of maximums (MoM) map can be generated which will show the worst possible scenario for a hurricane of a specific strength.[24]

The location of most tropical cyclone-related tornadoes is their northeast quadrant in the Northern Hemisphere and southeast quadrant in the Southern Hemisphere.[25] Like most of the other forecasts for tropical cyclone effects, an accurate track forecast is required in order to produce an accurate tornado threat forecast.

By looking at annual variations in various climate parameters, forecasters can make predictions about the overall number and intensity of tropical cyclones that will occur in a given season, for example, when constructing its seasonal outlooks, the Climate Prediction Center in the United States considers the effects of the El Niño-Southern Oscillation, 25–40 year tropical cycle, wind shear over the oceans, and ocean surface temperature.[26]

^Mooney, Chris (2007). "Chapter 4: Lay that Matrix Down". Storm World. Harcourt. p. 70. ISBN0-15-101287-3. ...1984...Gray also launched the endeavor that would make him most famous: a seasonal forecasting scheme for the Atlantic basin, which would predict the number of hurricanes and tropical storms months before their actual arrival. ... It's hard to overstate the breakthrough that Gray had achieved with his forecasting scheme.

1.
Tropical cyclone
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Depending on its location and strength, a tropical cyclone is referred to by names such as hurricane, typhoon /taɪˈfuːn/, tropical storm, cyclonic storm, tropical depression, and simply cyclone. A hurricane is a storm that occurs in the Atlantic Ocean and northeastern Pacific Ocean, a typhoon occurs in the northwestern Pacific Ocean, Tropical cyclones typically form over large bodies of relatively warm water. They derive their energy through the evaporation of water from the ocean surface and this energy source differs from that of mid-latitude cyclonic storms, such as noreasters and European windstorms, which are fueled primarily by horizontal temperature contrasts. The strong rotating winds of a tropical cyclone are a result of the conservation of momentum imparted by the Earths rotation as air flows inwards toward the axis of rotation. As a result, they form within 5° of the equator. Tropical cyclones are typically between 100 and 2,000 km in diameter, Tropical refers to the geographical origin of these systems, which form almost exclusively over tropical seas. Cyclone refers to their nature, with wind blowing counterclockwise in the Northern Hemisphere. The opposite direction of circulation is due to the Coriolis effect, in addition to strong winds and rain, tropical cyclones are capable of generating high waves, damaging storm surge, and tornadoes. They typically weaken rapidly over land where they are cut off from their energy source. For this reason, coastal regions are vulnerable to damage from a tropical cyclone as compared to inland regions. Heavy rains, however, can cause significant flooding inland, though their effects on human populations are often devastating, tropical cyclones can relieve drought conditions. They also carry heat away from the tropics and transport it toward temperate latitudes. Tropical cyclones are areas of low pressure in the troposphere. On Earth, the pressures recorded at the centers of tropical cyclones are among the lowest ever observed at sea level, the environment near the center of tropical cyclones is warmer than the surroundings at all altitudes, thus they are characterized as warm core systems. The near-surface wind field of a cyclone is characterized by air rotating rapidly around a center of circulation while also flowing radially inwards. At the outer edge of the storm, air may be nearly calm, however, due to the Earths rotation, as air flows radially inward, it begins to rotate cyclonically in order to conserve angular momentum. At an inner radius, air begins to ascend to the top of the troposphere and this radius is typically coincident with the inner radius of the eyewall, and has the strongest near-surface winds of the storm, consequently, it is known as the radius of maximum winds. Once aloft, air flows away from the center, producing a shield of cirrus clouds

2.
Tropical cyclogenesis
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Tropical cyclogenesis is the development and strengthening of a tropical cyclone in the atmosphere. The mechanisms through which tropical cyclogenesis occurs are distinctly different from those through which mid-latitude cyclogenesis occurs, tropical cyclogenesis involves the development of a warm-core cyclone, due to significant convection in a favorable atmospheric environment. Tropical cyclones tend to develop during the summer, but have been noted in every month in most basins. Climate cycles such as ENSO and the Madden–Julian oscillation modulate the timing, there is a limit on tropical cyclone intensity which is strongly related to the water temperatures along its path. An average of 86 tropical cyclones of tropical storm intensity form annually worldwide, of those,47 reach hurricane/typhoon strength, and 20 become intense tropical cyclones. While these conditions are necessary for tropical cyclone formation, they do not guarantee that a tropical cyclone will form. Normally, a temperature of 26.5 °C spanning through at least a 50-metre depth is considered the minimum to maintain the special mesocyclone that is the tropical cyclone. These warm waters are needed to maintain the core that fuels tropical systems. This value is well above 16.1 °C, the average surface temperature of the oceans. Tropical cyclones are known to even when normal conditions are not met. In a moist atmosphere, this rate is 6.5 °C/km, while in an atmosphere with less than 100% relative humidity. Under a cold cyclone,500 hPa temperatures can fall as low as −30 °C and this also explains why moisture in the mid-levels of the troposphere, roughly at the 500 hPa level, is normally a requirement for development. However, when dry air is found at the same height, at heights near the tropopause, the 30-year average temperature was −77 °C. A recent example of a cyclone that maintained itself over cooler waters was Epsilon of the 2005 Atlantic hurricane season. Emanuels model is called the maximum intensity, or MPI. Maps created from this equation show regions where tropical storm and hurricane formation is possible and this does not take into account vertical wind shear. A minimum distance of 500 km from the equator is normally needed for tropical cyclogenesis, the Coriolis force imparts rotation on the flow and arises as winds begin to flow in toward the lower pressure created by the pre-existing disturbance. The existence of a significant Coriolis force allows the developing vortex to achieve gradient wind balance, even with perfect upper level conditions and the required atmospheric instability, the lack of a surface focus will prevent the development of organized convection and a surface low

3.
Eye (cyclone)
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The eye is a region of mostly calm weather at the center of strong tropical cyclones. The eye of a storm is a circular area, typically 30–65 km in diameter. It is surrounded by the eyewall, a ring of towering thunderstorms where the most severe weather occurs, the cyclones lowest barometric pressure occurs in the eye and can be as much as 15 percent lower than the pressure outside the storm. In strong tropical cyclones, the eye is characterized by light winds and clear skies, surrounded on all sides by a towering, symmetric eyewall. In weaker tropical cyclones, the eye is well defined and can be covered by the central dense overcast. Weaker or disorganized storms may also feature an eyewall that does not completely encircle the eye or have an eye that features heavy rain. In all storms, however, the eye is the location of the minimum barometric pressure - where the atmospheric pressure at sea level is the lowest. A typical tropical cyclone will have an eye of approximately 30–65 km across, the eye may be clear or have spotty low clouds, it may be filled with low- and mid-level clouds, or it may be obscured by the central dense overcast. There is, however, very little wind and rain, especially near the center and this is in stark contrast to conditions in the eyewall, which contains the storms strongest winds. Due to the mechanics of a cyclone, the eye. While normally quite symmetric, eyes can be oblong and irregular, a large ragged eye is a non-circular eye which appears fragmented, and is an indicator of a weak or weakening tropical cyclone. An open eye is an eye which can be circular, but the eyewall does not completely encircle the eye, also indicating a weakening, both of these observations are used to estimate the intensity of tropical cyclones via Dvorak analysis. Eyewalls are typically circular, however, distinctly polygonal shapes ranging from triangles to hexagons occasionally occur. While typical mature storms have eyes that are a few miles across, rapidly intensifying storms can develop an extremely small, clear. Storms with pinhole eyes are prone to fluctuations in intensity. Small/minuscule eyes—those less than 10 nmi across—often trigger eyewall replacement cycles and this can take place anywhere from fifteen to hundreds of kilometers outside the inner eye. The storm then develops two concentric eyewalls, or an eye within an eye, in most cases, the outer eyewall begins to contract soon after its formation, which chokes off the inner eye and leaves a much larger but more stable eye. While the replacement cycle tends to weaken storms as it occurs and this may trigger another re-strengthen cycle of eyewall replacement

4.
Effects of tropical cyclones
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The main effects of tropical cyclones include heavy rain, strong wind, large storm surges at landfall, and tornadoes. The destruction from a tropical cyclone depends mainly on its intensity, its size, tropical cyclones act to remove forest canopy as well as change the landscape near coastal areas, by moving and reshaping sand dunes and causing extensive erosion along the coast. Even well inland, heavy rainfall can lead to mudslides and landslides in mountainous areas and their effects can be sensed over time by studying the concentration of the Oxygen-18 isotope within caves within the vicinity of cyclones paths being very hazardous to peoples life. After the cyclone has passed, devastation often continues, standing water can cause the spread of disease, and transportation or communication infrastructure may have been destroyed, hampering clean-up and rescue efforts. Nearly two million people have died due to tropical cyclones. Despite their devastating effects, tropical cyclones are also beneficial, by potentially bringing rain to dry areas, out at sea, ships take advantage of their known characteristics by navigating through their weaker, western half. When a cyclone hits it causes PST hazards, PST is an acronym standing for Primary, Secondary and Tertiary. A primary hazard involves destructive winds, debris and storm surge, Secondary hazard is flooding, fires and of course fresh water flooding. Finally Tertiary hazards involves food prices that go majorly up and other long term hazards like water poisoning, a mature tropical cyclone can release heat at a rate upwards of 6x1014 watts. Tropical cyclones on the open sea cause large waves, heavy rain, generally, after its passage, a tropical cyclone stirs up ocean water, lowering sea surface temperatures behind it. This cool wake can cause the region to be favorable for a subsequent tropical cyclone. On rare occasions, tropical cyclones may actually do the opposite, 2005s Hurricane Dennis blew warm water behind it, contributing to the unprecedented intensity of Hurricane Emily, which followed it closely. Hurricanes help to maintain the heat balance by moving warm, moist tropical air to the mid-latitudes. Were it not for the movement of heat poleward, the regions would be unbearably hot. Shipwrecks are common with the passage of tropical cyclones. Such shipwrecks can change the course of history, as well as influence art, a hurricane led to a victory of the Spanish over the French for control of Fort Caroline, and ultimately the Atlantic coast of North America, in 1565. The Sea Venture was wrecked near Bermuda in 1609 which led to the colonization of Bermuda, mariners have a way to safely navigate around tropical cyclones. They split tropical cyclones in two, based on their direction of motion, and maneuver to avoid the right segment of the cyclone in the Northern Hemisphere

5.
Storm surge
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Most casualties during tropical cyclones occur as the result of storm surges. The deadliest storm surge on record was the 1970 Bhola cyclone, the low-lying coast of the Bay of Bengal is particularly vulnerable to surges caused by tropical cyclones. The deadliest storm surge in the twenty-first century was caused by the Cyclone Nargis, the next deadliest in this century was caused by the Typhoon Haiyan, which killed more than 6,000 people in the central Philippines in 2013 and resulted in economic losses estimated at $14 billion. Louis, Diamondhead and Pass Christian in Mississippi, a high storm surge occurred in New York City from Hurricane Sandy in October 2012, with a high tide of 14 ft. The pressure effects of a tropical cyclone will cause the level in the open ocean to rise in regions of low atmospheric pressure. The rising water level will counteract the low pressure such that the total pressure at some plane beneath the water surface remains constant. This effect is estimated at a 10 mm increase in sea level for every millibar drop in atmospheric pressure, strong surface winds cause surface currents at a 45° angle to the wind direction, by an effect known as the Ekman Spiral. Wind stresses cause a phenomenon referred to as wind set-up, which is the tendency for water levels to increase at the downwind shore, intuitively, this is caused by the storm simply blowing the water towards one side of the basin in the direction of its winds. Because the Ekman Spiral effects spread vertically through the water, the effect is proportional to depth. The pressure effect and the wind set-up on an open coast will be driven into bays in the way as the astronomical tide. The Earths rotation causes the Coriolis effect, which bends currents to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. When this bend brings the currents into more contact with the shore it can amplify the surge. The effect of waves, while powered by the wind, is distinct from a storms wind-powered currents. Powerful wind whips up large, strong waves in the direction of its movement, although these surface waves are responsible for very little water transport in open water, they may be responsible for significant transport near the shore. When waves are breaking on a more or less parallel to the beach. The rainfall effect is experienced predominantly in estuaries, Hurricanes may dump as much as 12 in of rainfall in 24 hours over large areas, and higher rainfall densities in localized areas. As a result, watersheds can quickly surge water into the rivers that drain them and this can increase the water level near the head of tidal estuaries as storm-driven waters surging in from the ocean meet rainfall flowing from the estuary. This situation well exemplified by the southeast coast of Florida

6.
Tropical cyclone basins
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Traditionally, areas of tropical cyclone formation are divided into seven basins. The western Pacific is the most active and the north Indian the least active, an average of 86 tropical cyclones of tropical storm intensity form annually worldwide, with 47 reaching hurricane/typhoon strength, and 20 becoming intense tropical cyclones. This region includes the North Atlantic Ocean, the Caribbean Sea, tropical cyclone formation here varies widely from year to year, ranging from one to over twenty-five per year. Most Atlantic tropical storms and hurricanes form between June 1 and November 30, on average,11 named storms occur each season, with an average of 6 becoming hurricanes and 2 becoming major hurricanes. The climatological peak of activity is around September 10 each season, the United States Atlantic coast and Gulf Coast, Mexico, Central America, the Caribbean Islands, and Bermuda are frequently affected by storms in this basin. Venezuela, the 4 provinces of Atlantic Canada, and Atlantic Macaronesian islands also are occasionally affected, many of the more intense Atlantic storms are Cape Verde-type hurricanes, which form off the west coast of Africa near the Cape Verde islands. Hurricane Vince, which made landfall on the southwestern coast of Spain as a depression in October 2005, is the only known system to impact mainland Europe as a tropical cyclone. The Northeastern Pacific is the second most active basin and has the highest number of storms per unit area, the hurricane season runs between May 15 and November 30 each year, and encompasses the vast majority of tropical cyclone activity in the region. In the 1971–2005 period, there were an average of 15–16 tropical storms,9 hurricanes, storms that form here often affect western Mexico, and less commonly the Continental United States, or northern Central America. Tropical storms in 1939,1976 and 1997 brought gale-force winds to California, the CPHC previously tasked with monitoring tropical activity in the basin was originally known as the Joint Hurricane Warning Center, today it is called the Joint Typhoon Warning Center. Central Pacific hurricanes are rare and on average 4 to 5 storms form or move in this area annually, the Northwest Pacific Ocean is the most active basin on the planet, accounting for one-third of all tropical cyclone activity. Annually, an average of 25.7 tropical cyclones in the basin acquire tropical storm strength or greater, also, the basin occupies all the territory north of the equator and west of the International Date Line, including the South China Sea. The basin sees activity year-round, however, tropical activity is at its minimum in February, sometimes, tropical storms in this region affect Cambodia, Laos, Malaysia, Thailand and even Singapore. The coast of China sees the most landfalling tropical cyclones worldwide, the Philippines archipelago receives an average of 6–7 tropical cyclone landfalls per year. This basin is divided into two areas, the Bay of Bengal and the Arabian Sea, with the Bay of Bengal dominating, still, this basin is the most inactive worldwide, with only 4 to 6 storms per year. This basins season has a peak, one in April and May, before the onset of the monsoon. Although it is a basin, the deadliest tropical cyclones in the world have formed here, including the 1970 Bhola cyclone. Nations affected include India, Bangladesh, Sri Lanka, Thailand, Myanmar, rarely do tropical cyclones that form in this basin affect the Arabian Peninsula or Somalia, however, Cyclone Gonu caused heavy damage in Oman on the peninsula in 2007

7.
Regional Specialized Meteorological Center
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In addition some WMO member countries that lacked extensive forecasting capability requested that specialized pollutant transport and dispersion forecasts be provided during these emergencies. As a result, during 1989 Meteo-France, Environment Canada and the United Kingdoms Met Office were all set up as RSMCs under interim arrangements between the WMO and the IAEA. Under these arrangements Meteo-France provided global coverage with the UKMO as the center until each WMO region had at least two RSMCs for transport model products. This resulted in the WMO regions RA and RA IV having two RSMCs each which indicated the need to revise the interim arrangements. The new arrangements came into force in August 1994, with EC and NOAA responsible for the Americas, while MF, the Australian Bureau of Meteorology was subsequently made an RSMC on July 1,1995, while the Japan Meteorological Agency was made one in July 1997. C. The United States National Hurricane Center is responsible for the tracking of tropical cyclones within the Atlantic Ocean, the Japan Meteorological Agency is responsible for issuing advisories within the Western Pacific basin. The India Meteorological Department is responsible for tracking tropical cyclones within the North Indian Ocean, météo-France La Reunion is responsible for the issuing advisories and tracking of tropical cyclones, however, the naming of systems is deferred to the Mauritius and Madagascar weather services. Within the Australian region five tropical cyclone warning centres are responsible for the naming and tracking of tropical cyclones, three of these centres are run by and located within the Australian Bureau of Meteorology regional offices in Perth, Darwin and Brisbane and use one national list of names. The other two tropical cyclone warning centres in the Australian region are located in Port Moresby, Papua New Guinea and Jakarta, Indonesia

8.
Tropical cyclone observation
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Tropical cyclone observation has been carried out over the past couple of centuries in various ways. Recent studies have concentrated on studying hurricane impacts lying within rocks or near shore lake sediments, recent studies of the 18O and 13C isotopes found in stalagmites in Belize show that tropical cyclone events can leave markers that can be separated out on a week-by-week basis. The error rate of type of microanalysis was 1 error in 1,200 sampling points. Rocks contain certain isotopes of elements, known as natural tracers, by studying the calcium carbonate in coral rock, past sea surface temperature and hurricane information can be revealed. Lighter oxygen isotopes are left behind in coral during periods of heavy rainfall. Since storm surges sweep coastal sands with them as they progress inland, radiocarbon dating is then used to date the layers. Before the invention of the telegraph in the early to mid-19th century, news was as fast as the quickest horse, stage, normally, there was no advance warning of a tropical cyclone impact. The variability in typhoon landfalls in Guangdong mimics that observed in other paleoclimatic proxies from China, remarkably, the two periods of most frequent typhoon strikes in Guangdong coincide with two of the coldest and driest periods in northern and central China during the Little Ice Age. For centuries, people have sailed the oceans and seas. The worst of the cyclones over the open seas likely took those that observed them into the depths of the oceans, however, some did survive to report harrowing tales. Wind reports from ships at sea have become based on anemometers. This is important to note as the Beaufort Scale underestimates winds at higher wind speeds, as Christopher Landsea et al. point out, many tropical cyclones that formed on the open sea and did not affect any coast usually went undetected prior to satellite observation since the 1970s. They estimated an undercount bias of zero to six tropical cyclones per year between 1851 and 1885 and zero to four per year between 1886 and 1910. These undercounts roughly take into account the size of tropical cyclones, the density of shipping tracks over the Atlantic basin. In the early 20th century, forecasting the track of cyclones was still confined to areas of the greatest surface pressure falls, based upon surface weather observations and these methods proved to be the cutting edge of tropical cyclone forecasting through the mid 20th century. Land-based surface observations remain invaluable as a source of information at locations near the coastline. Combined with ship observations and newspapers, they formed the total information network for hurricane detection until radiosondes were introduced in 1941, land-based observations of pressure and wind can show how quickly a tropical cyclone is decaying as it moves inland. Their rainfall reports show where significant rainfall is occurring, and can be an alert for possible flooding, with the establishment of the ASOS network in the United States during the 1990s, more locations are reporting around the clock than ever before

9.
Tropical cyclone rainfall forecasting
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Tropical cyclone rainfall forecasting involves using scientific models and other tools to predict the precipitation expected in tropical cyclones such as hurricanes and typhoons. Knowledge of tropical cyclone rainfall climatology is helpful in the determination of a tropical cyclone rainfall forecast, more rainfall falls in advance of the center of the cyclone than in its wake. The heaviest rainfall falls within its central dense overcast and eyewall, slow moving tropical cyclones, like Hurricane Danny and Hurricane Wilma, can lead to the highest rainfall amounts due to prolonged heavy rains over a specific location. However, vertical wind shear leads to decreased rainfall amounts, as rainfall is favored downshear and slightly left of the center and the upshear side is left devoid of rainfall. A strong system moving through the mid latitudes, such as a front, can lead to high amounts from tropical systems. Movement of a cyclone over cool water will also limit its rainfall potential. A combination of factors can lead to high rainfall amounts. Use of forecast models can help determine the magnitude and pattern of the rainfall expected, climatology and persistence models, such as r-CLIPER, can create a baseline for tropical cyclone rainfall forecast skill. The forecast method of TRaP assumes that the structure the tropical cyclone currently has changes little over the next 24 hours. The global forecast model which shows the most skill in forecasting tropical cyclone-related rainfall in the United States is the GFS, a larger proportion of rainfall falls in advance of the center than after the centers passage, with the highest percentage falling in the right-front quadrant. A tropical cyclones highest rainfall rates can lie in the rear quadrant within a training inflow band. Rainfall is found to be strongest in their core, within a degree of latitude of the center. Most of the rainfall in hurricanes is concentrated within its radius of gale-force winds, larger tropical cyclones have larger rain shields, which can lead to higher rainfall amounts farther from the cyclones center. Storms which have moved slowly, or loop, lead to the highest rainfall amounts, riehl calculated that 33.97 inches of rainfall per day can be expected within one-half degree, or 35 miles, of the center of a mature tropical cyclone. This would be true over water, within 100 miles of the coastline, as a cyclone moves farther inland and is cut off from its supply of warmth and moisture, rainfall amounts from tropical cyclones and their remains decrease quickly. In other words, southwesterly shear forces the bulk of the rainfall north-northeast of the center, if the wind shear is strong enough, the bulk of the rainfall will move away from the center leading to what is known as an exposed circulation center. When this occurs, the magnitude of rainfall with the tropical cyclone will be significantly reduced. Surface fronts with precipitable water amounts of 1.46 inches or more, moist air forced up the slopes of coastal hills and mountain chains can lead to much heavier rainfall than in the coastal plain

10.
Tropical cyclone rainfall climatology
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A tropical cyclone rainfall climatology is developed to determine rainfall characteristics of past tropical cyclones. A tropical cyclone rainfall climatology can be used to help forecast current or upcoming tropical cyclone impacts, the degree of a tropical cyclone rainfall impact depends upon speed of movement, storm size, and degree of vertical wind shear. One of the most significant threats from tropical cyclones is heavy rainfall, large, slow moving, and non-sheared tropical cyclones produce the heaviest rains. Flooding from tropical cyclones remains a significant cause of fatalities, particularly in low-lying areas, while inland flooding is common to tropical cyclones, there are factors which lead to excessive rainfall from tropical cyclones. Slow motion, as was seen during Hurricane Danny and Hurricane Wilma, larger tropical cyclones drop more rainfall as they precipitate upon one spot for a longer time frame than average or small tropical cyclones. A combination of two of these factors could be especially crippling, as was seen during Hurricane Mitch in Central America, during the 2005 season, flooding related to slow-moving Hurricane Stans broad circulation led to 1, 662–2,000 deaths. Isaac Cline was the first to investigate rainfall distribution around tropical cyclones in the early 1900s and he found that a larger proportion of rainfall falls in advance of the center than after the centers passage, with the highest percentage falling in the right front quadrant. Father Viñes of Cuba found that some tropical cyclones have their highest rainfall rates in the rear quadrant within a training inflow band, normally, as a tropical cyclone intensifies, its heavier rainfall rates become more concentrated around its center. Most of the rainfall in tropical cyclones is concentrated within its radius of gale-force winds, Rainfall is more common near the center of tropical cyclones overnight. Over land, outer bands are more active during the heating of the day, recent studies have shown that half of the rainfall within a tropical cyclone is stratiform in nature. Local amounts can exceed this chart by a factor of two due to topography, wind shear tends to lessen the amounts below what is shown on the table. Larger tropical cyclones have larger rain shields, which can lead to higher rainfall amounts farther from the cyclones center and this is generally due to the longer time frame rainfall falls at any one spot in a larger system, when compared to a smaller system. Storms which have moved slowly, or loop, over a succession of lead to the highest rainfall amounts for several countries. Riehl calculated that 33.97 inches of rainfall per day can be expected within one-half degree, or 35 miles and this would be true over water, within 100 miles of the coastline, and outside topographic features. As a cyclone moves farther inland and is cut off from its supply of warmth and moisture, rainfall amounts from tropical cyclones, in other words, southwesterly shear forces the bulk of the rainfall north-northeast of the center. If the wind shear is strong enough, the bulk of the rainfall will move away from the leading to what is known as an exposed circulation center. When this occurs, the magnitude of rainfall with the tropical cyclone will be significantly reduced. The stronger the upper trough picking up the cyclone, the more significant the left of track shift in the rainfall distribution tends to be

11.
Tropical cyclone naming
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Tropical cyclones and subtropical cyclones are named by various warning centers to provide ease of communication between forecasters and the general public regarding forecasts, watches, and warnings. The names are intended to reduce confusion in the event of concurrent storms in the same basin, generally once storms produce sustained wind speeds of more than 33 knots, names are assigned in order from predetermined lists depending on which basin they originate. Before the formal start of naming, tropical cyclones were named after places, objects, the credit for the first usage of personal names for weather systems is generally given to the Queensland Government Meteorologist Clement Wragge, who named systems between 1887 and 1907. This system of naming weather systems subsequently fell into disuse for years after Wragge retired. Before the formal start of naming, tropical cyclones were named after places, objects. The credit for the first usage of names for weather systems is generally given to the Queensland Government Meteorologist Clement Wragge. This system of naming weather systems subsequently fell into disuse for years after Wragge retired until it was revived in the latter part of World War II for the Western Pacific. Formal naming schemes have subsequently introduced for the North Atlantic, Eastern, Central, Western and Southern Pacific basins as well as the Australian region. This is especially important when multiple storms are occurring simultaneously in the ocean basin. Names are generally assigned in order from predetermined lists, once they produce one, however, standards vary from basin to basin, with some systems named in the Western Pacific when they develop into tropical depressions or enter PAGASAs area of responsibility. Within the Southern Hemisphere, systems must be characterized by a significant amount of gale-force winds occurring around the center before they are named, PAGASA also retires the names of significant tropical cyclones when they have caused at least ₱1 billion in damage and/or have caused at least 300 deaths. There are six lists of names which rotate every six years and begin with the first letters A—W used, skipping Q and U, the names of significant tropical cyclones are retired from the lists, with a replacement name selected at the next World Meteorological Organizations Hurricane Committee meeting. If all of the names on a list are used, storms are named after the letters of the Greek alphabet, significant tropical cyclones have their names retired from the lists and a replacement name selected at the next World Meteorological Organization Hurricane Committee. When a tropical depression intensifies into a storm to the north of the Equator between the coastline of the Americas and 140°W, it will be named by the NHC. There are six lists of names which rotate every six years and begin with the letters A—Z used, skipping Q and U, the names of significant tropical cyclones are retired from the lists, with a replacement name selected at the next World Meteorological Organizations Hurricane Committee. If all of the names on a list are used, storms are named using the letters of the Greek alphabet, when a tropical depression intensifies into a tropical storm to the north of the Equator between 140°W and 180°, it is named by the CPHC. Significant tropical cyclones have their names retired from the lists, with a replacement name selected at the next Hurricane Committee meeting, Tropical cyclones that occur within the Northern Hemisphere between the anti-meridian and 100°E are officially named by the Japan Meteorological Agency when they become tropical storms. However, PAGASA also names tropical cyclones that occur or develop into tropical depressions within their area of responsibility between 5°N–25°N and 115°E-135°E

12.
History of tropical cyclone naming
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The practice of using names to identify tropical cyclones goes back several centuries, with storms named after places, saints or things they hit before the formal start of naming in each basin. Examples of such names are the 1911 Ship Cyclone, the 1928 Okeechobee hurricane, the system currently in place provides identification of tropical cyclones in a brief form that is easily understood and recognized by the public. This system of naming fell into disuse for years after Wragge retired. However, there has been controversy over the used at various times, with names being dropped for religious. Female names were used in the basins at various times between 1945 and 2000, and were the subject of several protests. At present tropical cyclones are named by one of eleven meteorological services. Due to the potential for longevity and multiple concurrent storms, the reduce the confusion about what storm is being described in forecasts, watches. Names are assigned in order from predetermined lists once storms have one, standards vary from basin to basin, with some tropical depressions named in the Western Pacific, while a significant amount of gale-force winds are required in the Southern Hemisphere. The practice of using names to tropical cyclones goes back several centuries, with systems named after places. Examples include the 1526 San Francisco hurricane, the 1928 Okeechobee hurricane, Wragge used names drawn from the letters of the Greek alphabet, Greek and Roman mythology and female names, to describe weather systems over Australia, New Zealand and the Antarctic. After the new Australian government had failed to create a weather bureau and appoint him director. This system of naming weather systems subsequently fell into disuse for years after Wragge retired. Wragges naming was also mentioned within Sir Napier Shaw’s “Manual of Meteorology” which likened it to a child naming waves, after reading about Clement Wragge, George Stewart was inspired to write a novel, Storm, about a storm affecting California which was named Maria. The book was read after it was published in 1941 by Random House, especially by United States Army Air Corps. During 1944, United States Army Air Forces forecasters at the newly established Saipan weather center, started to informally name typhoons after their wives and they also felt that using womens names was frivolous and that using the names in official communications would have made them look silly. During 1947 the Air Force Hurricane Office in Miami started using the Joint Army/Navy Phonetic Alphabet to name significant tropical cyclones in the North Atlantic Ocean. These names were used over the few years in private/internal communications between weather centres and aircraft, and were not included in public bulletins. As a result, during the tropical cyclone, Grady Norton decided to start using the names in public statements

13.
Royal Engineers
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The Corps of Royal Engineers, usually just called the Royal Engineers, and commonly known as the Sappers, is one of the corps of the British Army. It is highly regarded throughout the military, and especially the Army and it provides military engineering and other technical support to the British Armed Forces and is headed by the Chief Royal Engineer. The Regimental Headquarters and the Royal School of Military Engineering are in Chatham in Kent, the corps is divided into several regiments, barracked at various places in the United Kingdom and around the world. In Woolwich in 1716, the Board formed the Royal Regiment of Artillery and established a Corps of Engineers, the manual work was done by the Artificer Companies, made up of contracted civilian artisans and labourers. In 1782, a Soldier Artificer Company was established for service in Gibraltar, ten years later the Gibraltar company, which had remained separate, was absorbed and in 1812 the name was changed to the Corps of Royal Sappers and Miners. The Corps has no battle honours, in 1832, the regimental motto, Ubique Quo Fas Et Gloria Ducunt, was granted. The motto signified that the Corps had seen action in all the conflicts of the British Army. In 1911 the Corps formed its Air Battalion, the first flying unit of the British Armed Forces, the Air Battalion was the forerunner of the Royal Flying Corps and Royal Air Force. In 1915, in response to German mining of British trenches under the then static siege conditions of the First World War, before the Second World War, Royal Engineers recruits were required to be at least 5 feet 4 inches tall. They initially enlisted for six years with the colours and a six years with the reserve or four years. Unlike most corps and regiments, in which the age limit was 25. They trained at the Royal Engineers Depot in Chatham or the RE Mounted Depot at Aldershot, the Royal Engineers Museum is in Gillingham in Kent. Britain having acquired an Empire, it fell to the Royal Engineers to conduct some of the most significant civil engineering schemes around the world, some examples of great works of the era of empire can be found in A. J. Smitherss book Honourable Conquests. The Royal Engineers, Columbia Detachment, commanded by Richard Clement Moody, was responsible for the foundation, the Royal Albert Hall is one of the UKs most treasured and distinctive buildings, recognisable the world over. Since its opening by Queen Victoria in 1871, the leading artists from every kind of performance genre have appeared on its stage. The Hall was designed by Captain Francis Fowke and Major-General Henry Y. D. Scott of the Royal Engineers, the designers were heavily influenced by ancient amphitheatres, but had also been exposed to the ideas of Gottfried Semper while he was working at the Victoria and Albert Museum. Much of the British colonial era infrastructure of India, of which survive today, was created by engineers of the three presidencies armies and the Royal Engineers. In 1838 he designed and built sea defences for Vizagapatam and he masterminded the Godavery Delta project where 720,000 acres of land were irrigated and 500 miles of land to the port of Cocanada was made navigable in the 1840s

14.
Atmospheric pressure
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Atmospheric pressure, sometimes also called barometric pressure, is the pressure exerted by the weight of air in the atmosphere of Earth. In most circumstances atmospheric pressure is approximated by the hydrostatic pressure caused by the weight of air above the measurement point. As elevation increases, there is less overlying atmospheric mass, so that atmospheric pressure decreases with increasing elevation. On average, a column of air one square centimetre in cross-section, measured from sea level to the top of the atmosphere, has a mass of about 1.03 kilograms and that force is a pressure of 10.1 N/cm2 or 101 kN/m2. A column 1 square inch in cross-section would have a weight of about 14.7 lb or about 65.4 N and it is modified by the planetary rotation and local effects such as wind velocity, density variations due to temperature and variations in composition. The standard atmosphere is a unit of pressure defined as 101325 Pa, the mean sea level pressure is the average atmospheric pressure at sea level. This is the pressure normally given in weather reports on radio, television. When barometers in the home are set to match the weather reports, they measure pressure adjusted to sea level. The altimeter setting in aviation, is an atmospheric pressure adjustment, average sea-level pressure is 1013.25 mbar. In aviation weather reports, QNH is transmitted around the world in millibars or hectopascals, except in the United States, Canada, however, in Canadas public weather reports, sea level pressure is instead reported in kilopascals. The highest sea-level pressure on Earth occurs in Siberia, where the Siberian High often attains a sea-level pressure above 1050 mbar, the lowest measurable sea-level pressure is found at the centers of tropical cyclones and tornadoes, with a record low of 870 mbar. Pressure varies smoothly from the Earths surface to the top of the mesosphere, although the pressure changes with the weather, NASA has averaged the conditions for all parts of the earth year-round. As altitude increases, atmospheric pressure decreases, one can calculate the atmospheric pressure at a given altitude. Temperature and humidity affect the atmospheric pressure, and it is necessary to know these to compute an accurate figure. The graph at right was developed for a temperature of 15 °C, at low altitudes above the sea level, the pressure decreases by about 1.2 kPa for every 100 meters. See pressure system for the effects of air pressure variations on weather, Atmospheric pressure shows a diurnal or semidiurnal cycle caused by global atmospheric tides. This effect is strongest in tropical zones, with an amplitude of a few millibars and these variations have two superimposed cycles, a circadian cycle and semi-circadian cycle. The highest adjusted-to-sea level barometric pressure recorded on Earth was 1085.7 hPa measured in Tosontsengel

15.
Havana
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Havana is the capital city, largest city, province, major port, and leading commercial centre of Cuba. The city extends mostly westward and southward from the bay, which is entered through a narrow inlet, the sluggish Almendares River traverses the city from south to north, entering the Straits of Florida a few miles west of the bay. King Philip II of Spain granted Havana the title of City in 1592, walls as well as forts were built to protect the old city. The sinking of the U. S. battleship Maine in Havanas harbor in 1898 was the cause of the Spanish–American War. Contemporary Havana can essentially be described as three cities in one, Old Havana, Vedado and the suburban districts. The city is the center of the Cuban government, and home to various ministries, headquarters of businesses, the current mayor is Marta Hernández of the Communist Party of Cuba. In 2009, the city/province had the third highest income in the country, the city attracts over a million tourists annually, the Official Census for Havana reports that in 2010 the city was visited by 1,176,627 international tourists, a 20% increase from 2005. Old Havana was declared a UNESCO World Heritage Site in 1982, the city is also noted for its history, culture, architecture and monuments. As typical of Cuba, Havana also features a tropical climate, in May 2015, Havana was officially recognized as one of the New7Wonders Cities together with Vigan, Doha, La Paz, Durban, Beirut, and Kuala Lumpur. Most native settlements became the site of Spanish colonial cities retaining their original Taíno names, an alternate theory is that Habana is derived from the Middle Dutch word havene, referring to a harbour, etymologically related to the English word haven. All attempts to found a city on Cubas south coast failed, however, an early map of Cuba drawn in 1514 places the town at the mouth of this river. The town that became Havana finally originated adjacent to what was then called Puerto de Carenas, the quality of this natural bay, which now hosts Havanas harbor, warranted this change of location. Pánfilo de Narváez gave Havana – the sixth town founded by the Spanish on Cuba – its name, the name combines San Cristóbal, patron saint of Havana. Shortly after the founding of Cubas first cities, the served as little more than a base for the Conquista of other lands. Havana began as a port, and suffered regular attacks by buccaneers, pirates. The first attack and resultant burning of the city was by the French corsair Jacques de Sores in 1555, ships from all over the New World carried products first to Havana, in order to be taken by the fleet to Spain. The thousands of ships gathered in the bay also fueled Havanas agriculture and manufacture, since they had to be supplied with food, water. On December 20,1592, King Philip II of Spain granted Havana the title of City, later on, the city would be officially designated as Key to the New World and Rampart of the West Indies by the Spanish Crown

16.
Telegraph
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Telegraphy is the long-distance transmission of textual or symbolic messages without the physical exchange of an object bearing the message. Thus semaphore is a method of telegraphy, whereas pigeon post is not, telegraphy requires that the method used for encoding the message be known to both sender and receiver. Such methods are designed according to the limits of the medium used. The use of signals, beacons, reflected light signals. In the 19th century, the harnessing of electricity led to the invention of electrical telegraphy, the advent of radio in the early 20th century brought about radiotelegraphy and other forms of wireless telegraphy. The word telegraph was first coined by the French inventor of the Semaphore line, Claude Chappe, a telegraph is a device for transmitting and receiving messages over long distances, i. e. for telegraphy. The word telegraph alone now generally refers to an electrical telegraph, Wireless telegraphy is also known as CW, for continuous wave, as opposed to the earlier radio technique of using a spark gap. Contrary to the definition used by Chappe, Morse argued that the term telegraph can strictly be applied only to systems that transmit. This is to be distinguished from semaphore, which transmits messages. Smoke signals, for instance, are to be considered semaphore, according to Morse, telegraph dates only from 1832 when Pavel Schilling invented one of the earliest electrical telegraphs. A telegraph message sent by a telegraph operator or telegrapher using Morse code was known as a telegram. A cablegram was a sent by a submarine telegraph cable. Later, a Telex was a sent by a Telex network. A wire picture or wire photo was a picture that was sent from a remote location by a facsimile telegraph. A diplomatic telegram, also known as a cable, is the term given to a confidential communication between a diplomatic mission and the foreign ministry of its parent country. These continue to be called telegrams or cables regardless of the used for transmission. Commercial electrical telegraphs were introduced from 1837, the first telegraphs came in the form of optical telegraph, including the use of smoke signals, beacons, or reflected light, which have existed since ancient times. Early proposals for a telegraph system were made to the Royal Society by Robert Hooke in 1684 and were first implemented on an experimental level by Sir Richard Lovell Edgeworth in 1767

17.
Radio
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When radio waves strike an electrical conductor, the oscillating fields induce an alternating current in the conductor. The information in the waves can be extracted and transformed back into its original form, Radio systems need a transmitter to modulate some property of the energy produced to impress a signal on it, for example using amplitude modulation or angle modulation. Radio systems also need an antenna to convert electric currents into radio waves, an antenna can be used for both transmitting and receiving. The electrical resonance of tuned circuits in radios allow individual stations to be selected, the electromagnetic wave is intercepted by a tuned receiving antenna. Radio frequencies occupy the range from a 3 kHz to 300 GHz, a radio communication system sends signals by radio. The term radio is derived from the Latin word radius, meaning spoke of a wheel, beam of light, however, this invention would not be widely adopted. The switch to radio in place of wireless took place slowly and unevenly in the English-speaking world, the United States Navy would also play a role. Although its translation of the 1906 Berlin Convention used the terms wireless telegraph and wireless telegram, the term started to become preferred by the general public in the 1920s with the introduction of broadcasting. Radio systems used for communication have the following elements, with more than 100 years of development, each process is implemented by a wide range of methods, specialised for different communications purposes. Each system contains a transmitter, This consists of a source of electrical energy, the transmitter contains a system to modulate some property of the energy produced to impress a signal on it. This modulation might be as simple as turning the energy on and off, or altering more subtle such as amplitude, frequency, phase. Amplitude modulation of a carrier wave works by varying the strength of the signal in proportion to the information being sent. For example, changes in the strength can be used to reflect the sounds to be reproduced by a speaker. It was the used for the first audio radio transmissions. Frequency modulation varies the frequency of the carrier, the instantaneous frequency of the carrier is directly proportional to the instantaneous value of the input signal. FM has the capture effect whereby a receiver only receives the strongest signal, Digital data can be sent by shifting the carriers frequency among a set of discrete values, a technique known as frequency-shift keying. FM is commonly used at Very high frequency radio frequencies for high-fidelity broadcasts of music, analog TV sound is also broadcast using FM. Angle modulation alters the phase of the carrier wave to transmit a signal

18.
Radiosonde
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Modern radiosondes measure or calculate the following variables, altitude, pressure, temperature, relative humidity, wind, cosmic ray readings at high altitude and geographical position. Radiosondes measuring ozone concentration are known as ozonesondes, radiosondes may operate at a radio frequency of 403 MHz or 1680 MHz. A radiosonde whose position is tracked as it ascends to give wind speed, most radiosondes have radar reflectors and are technically rawinsondes. A radiosonde that is dropped from an airplane and falls, rather than being carried by a balloon is called a dropsonde, radiosondes are an essential source of meteorological data, and hundreds are launched all over the world daily. This proved to be difficult because the kites were linked to the ground and were difficult to manoeuvre in gusty conditions. Furthermore, the sounding was limited to low altitudes because of the link to the ground, gustave Hermite and Georges Besançon, from France, were the first in 1892 to use a balloon to fly the meteograph. In 1898, Léon Teisserenc de Bort organized at the Observatoire de Météorologie Dynamique de Trappes the first regular use of these balloons. Data from these launches showed that the temperature lowered with height up to an altitude, which varied with the season. De Borts discovery of the tropopause and stratosphere was announced in 1902 at the French Academy of Sciences, other researchers, like Richard Aßmann and William Henry Dines, were working at the same times with similar instruments. In 1924, Colonel William Blaire in the U. S. Signal Corps did the first primitive experiments with weather measurements from balloon, the first true radiosonde that sent precise encoded telemetry from weather sensors was invented in France by Robert Bureau. Bureau coined the name radiosonde and flew the first instrument on January 7,1929, developed independently a year later, Pavel Molchanov flew a radiosonde on January 30,1930. Molchanovs design became a popular standard because of its simplicity and because it converted sensor readings to Morse code, working with a modified Molchanov sonde, Sergey Vernov was the first to use radiosondes to perform cosmic ray readings at high altitude. On April 1,1935, he took measurements up to 13.6 km using a pair of Geiger counters in a circuit to avoid counting secondary ray showers. The sondes were tracked for two days, a rubber or latex balloon filled with either helium or hydrogen lifts the device up through the atmosphere. The maximum altitude to which the balloon ascends is determined by the diameter, balloon sizes can range from 100 to 3,000 g. As the balloon ascends through the atmosphere, the pressure decreases, eventually, the balloon will expand to the extent that its skin will break, terminating the ascent. An 800 g balloon will burst at about 21 km, after bursting, a small parachute on the radiosondes support line carries it to Earth. A typical radiosonde flight lasts 60 to 90 minutes, one radiosonde from Clark Air Base, Philippines, reached an altitude of 155,092 ft

19.
Hurricane hunters
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The Hurricane Hunters are aircrews that fly into tropical cyclones in the North Atlantic Ocean and Northeastern Pacific Ocean to gather weather data. One U. S. aircrew has been lost in duty since such missions began in 1943, six of the seven crew members of the Navy PB4Y-2 were killed on October 1,1945 when their plane went down in a Category 1 typhoon over the South China Sea. Before satellites were used to find storms, military aircraft flew routine weather reconnaissance tracks to detect formation of tropical cyclones, the term hurricane hunters was first applied to its missions in 1946. The computer models that forecast hurricane tracks and intensity mainly use G-IV dropwindsonde data collected day, among the types of aircraft that have been used to investigate hurricanes, are an instrumented Lockheed U-2 flown in Hurricane Ginny during the 1963 Atlantic hurricane season. Other types include the A-20 Havoc,1944, B-24, 1944–1945, B-17, 1945–1947, B-25, 1946–1947, B-29, wB-29, 1951–1956, WB-50, 1956–1963, WB-47, 1963–1969, WC-121N 1954-1973, WC-130A, B, E, H, 1965-2012. The idea of reconnaissance of hurricane storm trackers was put forth by Captain W. L. Farnsworth of the Galveston Commercial Association in the early 1930s. Supported by the United States Weather Bureau, the storm patrol bill passed both the United States Senate and United States House of Representatives on June 15,1936. The 1943 Surprise Hurricane, which struck Houston, Texas, during World War II and that summer, British pilots were being trained in instrument flying at Bryan Field. When they saw that the Americans were evacuating their AT-6 Texan trainers in the face of the storm, lead instructor Colonel Joe Duckworth took one of the trainers out and flew it straight into the eye of the storm. After he returned safely with navigator Lt. Ralph OHair, the weather officer, Lt. William Jones-Burdick, took over the navigators seat. This flight showed that hurricane reconnaissance flights were possible, and further flights continued occasionally, in 1946, the moniker Hurricane Hunters was first used, and the Air Force and now Air Force Reserve have used it ever since. The United States Navys VW-4 / WEARECORON FOUR Weather Reconnaissance Squadron Four and they flew several types of aircraft, but the WC-121N Willy Victor was the aircraft most often associated with flying into the eye of the storm. The squadron operated WC-121s between late 1954 and 1972, VW-4 lost one aircraft and crew in a penetration of Hurricane Janet, and another to severe damage in a storm, but the severely damaged Willy Victor brought her crew home, though it never flew again. During 1973-1975, VW-4 operated the turbine-propeller Lockheed WP-3A Orion, in 1974, a newly converted WC-130 was transferred to the 54th Weather Reconnaissance Squadron, the Typhoon Chasers, at Andersen Air Force Base on Guam. The aircraft was sent to investigate Typhoon Bess, the crew departed Clark Air Base in the Philippines with the callsign Swan 38. Radio contact with the aircraft was lost on 12 October 1974, there were no radio transmissions indicating an emergency on board, and search teams could not locate the aircraft or its crew. All six crew members were listed as killed in action, Swan 38 was the only WC-130 lost in a storm. The landfall of Hurricane Katrina on 29 August 2005 devastated Keesler Air Force Base, the equipment and personnel of the squadron were flying out of Dobbins Air Reserve Base near Atlanta

20.
Weather radar
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Weather radar, also called weather surveillance radar and Doppler weather radar, is a type of radar used to locate precipitation, calculate its motion, and estimate its type. Modern weather radars are mostly pulse-Doppler radars, capable of detecting the motion of rain droplets in addition to the intensity of the precipitation, both types of data can be analyzed to determine the structure of storms and their potential to cause severe weather. During World War II, radar operators discovered that weather was causing echoes on their screen, techniques were developed to filter them, but scientists began to study the phenomenon. Soon after the war, surplus radars were used to detect precipitation, since then, weather radar has evolved on its own and is now used by national weather services, research departments in universities, and in television newscasts. Raw images are used and specialized software can take radar data to make short term forecasts of future positions and intensities of rain, snow, hail. Radar output is even incorporated into weather prediction models to improve analyses. During World War II, military radar operators noticed noise in returned echoes due to rain, snow, after the war, military scientists returned to civilian life or continued in the Armed Forces and pursued their work in developing a use for those echoes. In the United States, David Atlas, at first working for the Air Force and later for MIT, Marshall and R. H. Douglas formed the Stormy Weather Group in Montreal. By 1950 the UK company EKCO was demonstrating its airborne cloud, in 1953 Donald Staggs, an electrical engineer working for the Illinois State Water Survey, made the first recorded radar observation of a hook echo associated with a tornadic thunderstorm. Between 1950 and 1980, reflectivity radars, which measure position, the early meteorologists had to watch a cathode ray tube. During the 1970s, radars began to be standardized and organized into networks, the first devices to capture radar images were developed. The number of scanned angles was increased to get a view of the precipitation, so that horizontal cross-sections. Studies of the organization of thunderstorms were then possible for the Alberta Hail Project in Canada, the NSSL, created in 1964, began experimentation on dual polarization signals and on Doppler effect uses. In May 1973, a tornado devastated Union City, Oklahoma, for the first time, a Dopplerized 10 cm wavelength radar from NSSL documented the entire life cycle of the tornado. The researchers discovered a mesoscale rotation in the cloud aloft before the tornado touched the ground – the tornadic vortex signature, NSSLs research helped convince the National Weather Service that Doppler radar was a crucial forecasting tool. The Super Outbreak of tornadoes on 3–4 April 1974 and their devastating destruction might have helped to get funding for further developments, between 1980 and 2000, weather radar networks became the norm in North America, Europe, Japan and other developed countries. Conventional radars were replaced by Doppler radars, which in addition to position, in the United States, the construction of a network consisting of 10 cm radars, called NEXRAD or WSR-88D, was started in 1988 following NSSLs research. In Canada, Environment Canada constructed the King City station, with a 5 cm research Doppler radar, by 1985 and this led to a complete Canadian Doppler network between 1998 and 2004

21.
Atlantic hurricane
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An Atlantic hurricane or tropical storm is a tropical cyclone that forms in the Atlantic Ocean, usually in the summer or fall. A hurricane differs from a cyclone or typhoon only on the basis of location, a hurricane is a storm that occurs in the Atlantic Ocean and northeastern Pacific Ocean, a typhoon occurs in the northwestern Pacific Ocean, and a cyclone occurs in the south Pacific or Indian Ocean. Tropical cyclones can be categorized by intensity, Tropical storms have one-minute maximum sustained winds of at least 39 mph, while hurricanes have one-minute maximum sustained winds exceeding 74 mph. Most North Atlantic tropical storms and hurricanes form between June 1 and November 30, in recent times, tropical disturbances that reach tropical storm intensity are named from a predetermined list. On average, in the North Atlantic basin 11.3 named storms occur each season, the climatological peak of activity is around September 11 each season. In March 2004, Catarina was the first hurricane-intensity tropical cyclone recorded in the Southern Atlantic Ocean. Tropical cyclones are steered by the flow throughout the depth of the troposphere. Specifically, air flow around high pressure systems and toward low pressure areas influence hurricane tracks, south of the subtropical ridge, surface easterly winds prevail. If the subtropical ridge is weakened by a trough, a tropical cyclone may turn poleward and then recurve. Poleward of the ridge, westerly winds prevail and generally steer tropical cyclones that reach northern latitudes toward the east. The westerlies also steer extratropical cyclones with their cold and warm fronts from west to east, generally speaking, the intensity of a tropical cyclone is determined by either the storms maximum sustained winds or lowest barometric pressure. The following table lists the most intense Atlantic hurricanes in terms of their lowest barometric pressure, in terms of wind speed, Hurricane Allen was the strongest Atlantic tropical cyclone on record, with maximum sustained winds of 190 mph. However, these measurements are suspect since instrumentation used to document wind speeds at the time would likely succumb to winds of such intensity, nonetheless, their central pressures are low enough to rank them among the strongest recorded Atlantic hurricanes. Owing to their intensity, the strongest Atlantic hurricanes have all attained Category 5 classification, Hurricane Opal, the strongest Category 4 hurricane recorded, intensified to reach a minimum pressure of 916 mbar, a pressure typical of Category 5 hurricanes. Nonetheless, the pressure remains too high to list Opal as one of the ten strongest Atlantic tropical cyclones, however, this was later superseded by Hurricane Patricia in 2015 in the east Pacific, which had a pressure reading of 872 mbar. Preceding Wilma is Hurricane Gilbert, which had held the record for most intense Atlantic hurricane for 17 years. The 1935 Labor Day hurricane, with a pressure of 892 mbar, is the third strongest Atlantic hurricane, since the measurements taken during Wilma and Gilbert were documented using dropsonde, this pressure remains the lowest measured over land. However, with a pressure of 895 mbar, Rita is the strongest tropical cyclone ever recorded in the Gulf of Mexico

22.
Sahel
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The Sahel is the ecoclimatic and biogeographic zone of transition in Africa between the Sahara to the north and the Sudanian Savanna to the south. Having a semi-arid climate, it stretches across the south-central latitudes of Northern Africa between the Atlantic Ocean and the Red Sea, the Arabic word sāḥil literally means shore, coast, while the word Sahara is derived from the Arabic word for desert. Together, these names evoke an image of the Sahels vegetation as a coastline on the Saharas ocean of sand, historically, the western part of the Sahel was sometimes known as the Sudan region. This belt was roughly located between the Sahara and the areas of West Africa. It is an ecoregion of semi-arid grasslands, savannas, steppes. The topography of the Sahel is mainly flat, most of the region lies between 200 and 400 meters in elevation, several isolated plateaus and mountain ranges rise from the Sahel, but are designated as separate ecoregions because their flora and fauna are distinct from the surrounding lowlands. Annual rainfall varies from around 100–200 mm in the north of the Sahel to around 600 mm in the south, the Sahel is mostly covered in grassland and savanna, with areas of woodland and shrubland. Grass cover is continuous across the region, dominated by annual grass species such as Cenchrus biflorus, Schoenefeldia gracilis. Species of acacia are the dominant trees, with Acacia tortilis the most common, along with Acacia senegal, other tree species include Commiphora africana, Balanites aegyptiaca, Faidherbia albida, and Boscia senegalensis. In the northern part of the Sahel, areas of shrub, including Panicum turgidum and Aristida sieberana, alternate with areas of grassland. During the long dry season, many lose their leaves. The larger species have greatly reduced in number by over-hunting and competition with livestock. The seasonal wetlands of the Sahel are important for birds moving within Africa. The Sahel has a tropical, hot steppe climate, the climate is typically hot, sunny, dry and somewhat windy all year long. The Sahels climate is similar to, but less extreme than, the Sahel mainly receives a low to a very low amount of precipitation annually. The steppe has a long, prevailing dry season and a short rainy season. The precipitation is extremely irregular, and varies considerably from season to season. Most of the rain falls during only one or two months, while the other months may remain absolutely dry

23.
Quasi-biennial oscillation
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The quasi-biennial oscillation is a quasiperiodic oscillation of the equatorial zonal wind between easterlies and westerlies in the tropical stratosphere with a mean period of 28 to 29 months. The alternating wind regimes develop at the top of the lower stratosphere, downward motion of the easterlies is usually more irregular than that of the westerlies. The amplitude of the phase is about twice as strong as that of the westerly phase. At the top of the vertical QBO domain, easterlies dominate, while at the bottom, westerlies are more likely to be found. At the 30mb level, with regards to monthly mean zonal winds, in 1883, the eruption of Krakatoa led to visual tracking of subsequent volcanic ash in the stratosphere. This visual tracking led to the discovery of easterly winds between 25 and 30 km above the surface, the winds were then called the Krakatau easterlies. In 1908, data balloons launched above Lake Victoria in Africa recorded westerly winds in the levels of the atmosphere. These findings, at the time, were thought to contradict the 1883 findings, however, the winds that would become known as the QBO were discovered to oscillate between westerly and easterly in the 1950s by researchers at the UK Meteorological Office. The cause of these QBO winds remained unclear for some time, radiosonde soundings showed that its phase was not related to the annual cycle, as is the case for many other stratospheric circulation patterns. The FU Berlin supplies a QBO data set that comprises rawinsonde observations from Canton Island, Gan, the plot below shows the QBO during the 1980s. The lack of a reliable QBO cycle deprives forecasters of a valuable tool, since the QBO has a strong influence on the North Atlantic Oscillation and thereby north European weather, scientists speculate that the coming winter could be warmer and stormier in that region. NASA Scientists have been researching to test if the extremely strong El Nino event of 2015/16, climate change and they are trying to determine if this is more of a once in a generation event, or if this is a sign of the changing climate. North Atlantic oscillation The Berlin QBO data series

24.
Christopher Landsea
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He is a member of the American Geophysical Union and the American Meteorological Society. Landsea earned his degree in Atmospheric Science at Colorado State University. He served as chair of the American Meteorological Societys Committee on Tropical Meteorology, Landsea was recognized with the American Meteorlogical Societys Banner I. Miller award for best contribution to the science of hurricane and tropical weather forecasting. Over the years Landseas work has involved the general hurricane FAQ currently on the Atlantic Oceanographic and Meteorological Laboratory website, Landsea has contributed to Science, Bulletin of the American Meteorological Society, Journal of Climate, and Nature. He has been vocal on the lack of a link between global warming and current hurricane intensity change, Landsea has published a number of research papers on cyclones and hurricanes. He is the author of Hurricanes, Typhoons, and Tropical Cyclones and he also has been the lead scientist in the Atlantic hurricane reanalysis since 1997. Landsea claimed the IPCC had become politicized and the leadership ignored his concerns, Landsea does not believe that global warming has a strong influence on hurricanes, global warming might be enhancing hurricane winds, but only by 1 percent or 2 percent. The question is whether were seeing any real increases in the hurricane activity and he went on to say with the Atlantic hurricanes in particular, theyre due to changes both in the ocean as well as the atmosphere. Just changing the ocean where its a bit warmer isnt sufficient. Miller Award for the best contribution to the science of hurricane, christopher Landsea biography page Q & A for NHC - Chris Landsea

25.
Tropical cyclone track forecasting
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Tropical cyclone track forecasting involves predicting where a tropical cyclone is going to track over the next five days, every 6 to 12 hours. The history of tropical cyclone track forecasting has evolved from an approach to a comprehensive approach which uses a variety of meteorological tools. Accurate track predictions depend on determining the position and strength of high- and low-pressure areas, computer forecast models are used to help determine this motion as far out as five to seven days in the future. The methods through which tropical cyclones are forecast have changed with the passage of time, the first known forecasts in the Western Hemisphere were made by Lt. Col. William Reed of the Corps of Royal Engineers at Barbados in 1847. Reed mostly utilized barometric pressure measurements as the basis of his forecasts, benito Viñes, S. J. introduced a forecast and warning system based on cloud cover changes in Havana during the 1870s. Forecasting hurricane motion was based on movements, as well as cloud. In 1895, it was noted that cool conditions with high pressure preceded tropical cyclones in the West Indies by several days. Before the early 1900s, most forecasts were done by direct observations at weather stations and it was not until the advent of radio in the early twentieth century that observations from ships at sea were available to forecasters. Despite the issuance of watches and warnings for systems threatening the coast. In 1937, radiosondes were used to tropical cyclone forecasting. In the 1950s, coastal weather radars began to be used in the United States, the launch of the first weather satellite, TIROS-I, in 1960, introduced new techniques to tropical cyclone forecasting that remain important to the present day. In the 1970s, buoys were introduced to improve the resolution of surface measurements, the ocean swell will slowly increase in height and frequency the closer a tropical cyclone gets to land. Two days in advance of the passage, winds go calm as the tropical cyclone interrupts the environmental wind flow. Within 36 hours of the passage, the pressure begins to fall. Within 18 hours of the approach, squally weather is common. Winds increase within 12 hours of the approach, occasionally reaching hurricane force. The oceans surface becomes whipped with foam, small items begin flying in the wind. Within 6 hours of the arrival, rain becomes continuous

26.
Tropical cyclone forecast model
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A tropical cyclone forecast model is a computer program that uses meteorological data to forecast aspects of the future state of tropical cyclones. There are three types of models, statistical, dynamical, or combined statistical-dynamic, dynamical models utilize powerful supercomputers with sophisticated mathematical modeling software and meteorological data to calculate future weather conditions. Statistical models forecast the evolution of a cyclone in a simpler manner, by extrapolating from historical datasets. Statistical-dynamical models use aspects of both types of forecasting, four primary types of forecasts exist for tropical cyclones, track, intensity, storm surge, and rainfall. Dynamical models were not developed until the 1970s and the 1980s, track models did not show forecast skill when compared to statistical models until the 1980s. Statistical-dynamical models were used from the 1970s into the 1990s, early models use data from previous model runs while late models produce output after the official hurricane forecast has been sent. The use of consensus, ensemble, and superensemble forecasts lowers errors more than any individual forecast model, both consensus and superensemble forecasts can use the guidance of global and regional models runs to improve the performance more than any of their respective components. Techniques used at the Joint Typhoon Warning Center indicate that superensemble forecasts are a powerful tool for track forecasting. The first statistical guidance used by the National Hurricane Center was the Hurricane Analog Technique and it used the newly developed North Atlantic tropical cyclone database to find storms with similar tracks. It then shifted their tracks through the current path, and used location, direction and speed of motion. The method did well with storms south of the 25th parallel which had not yet turned northward, since 1972, the Climatology and Persistence statistical model has been used to help generate tropical cyclone track forecasts. In the era of skillful dynamical forecasts, CLIPER is now being used as the baseline to show model, the Statistical Hurricane Intensity Forecast has been used since 1979 for tropical cyclone intensity forecasting. The version of SHIPS with an inland decay component is known as Decay SHIPS, the Logistic Growth Equation Model uses the same input as SHIPS but within a simplified dynamical prediction system. It has been operational since 2004, during 1972, the first model to forecast storm surge along the continental shelf of the United States was developed, known as the Special Program to List the Amplitude of Surges from Hurricanes. In 1978, the first hurricane-tracking model based on atmospheric dynamics – the movable fine-mesh model – began operating, the Quasi-Lagrangian Limited Area model is a multi-level primitive equation model using a Cartesian grid and the Global Forecasting System for boundary conditions. In the early 1980s, the assimilation of satellite-derived winds from water vapor, infrared, the Geophysical Fluid Dynamics Laboratory hurricane model was used for research purposes between 1973 and the mid-1980s. The larger the cyclone, the larger the impact of the effect is likely to be. For a weak hurricane without well-developed central thunderstorm activity, BAMS works well, large differences between model predictions can also indicate wind shear in the atmosphere, which could affect the intensity forecast as well

27.
Synoptic scale meteorology
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The synoptic scale in meteorology is a horizontal length scale of the order of 1000 kilometres or more. This corresponds to a horizontal scale typical of mid-latitude depressions, most high and low-pressure areas seen on weather maps such as surface weather analyses are synoptic-scale systems, driven by the location of Rossby waves in their respective hemisphere. Low-pressure areas and their related frontal zones occur on the edge of a trough within the Rossby wave pattern. Most precipitation areas occur near frontal zones, the word synoptic is derived from the Greek word συνοπτικός, meaning seen together. The Navier–Stokes equations applied to atmospheric motion can be simplified by scale analysis in the synoptic scale and it can be shown that the main terms in horizontal equations are Coriolis force and pressure gradient terms, therefore, one can use geostrophic approximation. In vertical coordinates, the equation simplifies to the hydrostatic equilibrium equation. The first weather maps in the 19th century were drawn well after the fact to help devise a theory on storm systems, use of surface analyses began first in the United States, spreading worldwide during the 1870s. Use of the Norwegian cyclone model for frontal analysis began in the late 1910s across Europe, surface weather analyses have special symbols which show frontal systems, cloud cover, precipitation, or other important information. For example, an H represents high pressure, implying good, an L represents low pressure, which frequently accompanies precipitation. Various symbols are used not just for frontal zones and other surface boundaries on weather maps, areas of precipitation help determine the frontal type and location. Mesoscale systems and boundaries such as cyclones, outflow boundaries. Isobars are commonly used to place surface boundaries from the horse latitudes poleward, the descriptor extratropical refers to the fact that this type of cyclone generally occurs outside of the tropics, in the middle latitudes of the planet. These are the phenomena which along with anti-cyclones, drive the weather over much of the Earth. An extratropical cyclone can transform into a storm, and from there into a tropical cyclone, if it dwells over warm waters and develops central convection. High-pressure systems are associated with light winds at the surface and subsidence through the lower portion of the troposphere. Subsidence will generally dry out an air mass by adiabatic, or compressional, thus, high pressure typically brings clear skies. During the day, since no clouds are present to reflect sunlight, there is more incoming solar radiation. At night, the absence of means that outgoing longwave radiation is not absorbed

28.
Hurricane Rita
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Hurricane Rita was the fourth-most intense Atlantic hurricane ever recorded and the most intense tropical cyclone ever observed in the Gulf of Mexico. Rita formed near The Bahamas from a wave on September 18 that originally developed off the coast of West Africa. It moved westward, and after passing through the Florida Straits, moving west-northwest, it rapidly intensified to reach peak winds of 180 mph, achieving Category 5 status on September 21st. Rapidly weakening over land, Rita degenerated into a large area over the lower Mississippi Valley by September 26th. Parishes in Southwest Louisiana and counties in Southeast Texas where Rita made landfall suffered from catastrophic-to-severe flooding, according to an October 25,2005 Disaster Center report,4,526 single-family dwellings were destroyed in Orange and Jefferson counties located in Southeast Texas. Major damage was sustained by 14,256 additional single-family dwellings, mobile homes and apartments also sustained significant damage or total destruction. In all, nine Texas counties and five Louisiana Parishes were declared disaster areas after the storm, electric service was disrupted in some areas of both Texas and Louisiana for several weeks. Texas reported the most deaths from the hurricane, where 113 deaths were reported,107 of which were associated with the evacuation of the Houston metropolitan area, moderate to severe damage was reported across the lower Mississippi Valley. Rainfall from the storm and its associated remnants extended from Louisiana to Michigan, rainfall peaked at 16.00 in in Central Louisiana. Several tornadoes were also associated with the hurricane and its subsequent remnants, throughout the path of Rita, damage totaled about $12 billion. As many as 120 deaths in four U. S. states were directly related to the hurricane, on September 7,2005, a tropical wave emerged off the west coast of Africa and moved westward into the Atlantic Ocean. Failing to produce organized, deep convection, the disturbance was not monitored by the National Hurricane Center for tropical cyclogenesis. Convection associated with the system increased briefly late on September 13 before dissipating shortly thereafter, at roughly the same time, a remnant surface trough had developed from a dissipating stationary front and began to drift westward north of the Lesser Antilles. Meanwhile, the wave slowly became better organized and was first noted in the NHCs Tropical Weather Outlooks on September 15 while northeast of Puerto Rico. The wave merged with the surface trough two days later, triggering an increase in activity and organization. At the time, the disturbance, classified as Tropical Depression Eighteen, was roughly 80 mi east of Grand Turk Island in the Turks, as a result, the tropical storm was named Rita. Once the upper-level low weakened, Ritas center of circulation reformed to the north, consequently, the tropical storm resumed its previous strengthening trend as it was steered westward across The Bahamas along the south periphery of a ridge. Upon entering the Straits of Florida on September 20, Rita strengthened into a Category 1 hurricane by 1200 UTC, six hours later, Rita intensified further into Category 2 before subsequently passing approximately 45 mi south of Key West, Florida

29.
Sailor
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A sailor, seaman, mariner, or seafarer is a person who navigates waterborne vessels or assists as a crewmember in their operation and maintenance. The term bluejacket may be used for British or US Navy enlisted sailors, the Bluejackets Manual is the basic handbook for United States Navy personnel. 700,000 of the worlds mariners come from the Philippines, the term seaman is frequently used in the particular sense of a sailor who is not an officer. Seafarers hold a variety of professions and ranks, each of which carries unique responsibilities which are integral to the operation of an ocean-going vessel. A ships crew can generally be divided into four categories, the deck department, the engineering department, the stewards department. Officer positions in the department include but are not limited to, master and his chief, second. The official classifications for unlicensed members of the department are able seaman. With some variation, the mate is most often charged with the duties of cargo mate. Second Mates are charged with being the officer in case of medical emergency. All three mates each do four-hour morning and afternoon shifts on the bridge, when underway at sea, Marine engineering staff also deal with the hotel facilities on board, notably the sewage, lighting, air conditioning and water systems. Engineering staff manage bulk fuel transfers, from a barge in port. When underway at sea, the second and third engineers will often be occupied with oil transfers from storage tanks, cleaning of oil purifiers is another regular task. Engineering staff are required to have training in firefighting and first aid, additional duties include maintaining the ships boats and performing other nautical tasks. Engineers play a key role in cargo loading/discharging gear and safety systems, though the specific cargo discharge function remains the responsibility of deck officers, other possible positions include motorman, machinist, electrician, refrigeration engineer and tankerman. A typical stewards department for a ship is a chief steward, a chief cook. All three positions are filled by unlicensed personnel. The chief steward also plans menus, compiles supply, overtime, the steward may requisition or purchase stores and equipment. A chief stewards duties may overlap with those of the assistant, the chief cook

30.
Storm
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A storm is any disturbed state of an environment or astronomical bodys atmosphere especially affecting its surface, and strongly implying severe weather. Heavy snowfall can allow special recreational activities to take place which would not be possible otherwise, the English word comes from Proto-Germanic *sturmaz meaning noise, tumult. Storms are created when a center of low pressure develops with a system of high pressure surrounding it and this combination of opposing forces can create winds and result in the formation of storm clouds, such as the cumulonimbus. Small localized areas of low pressure can form from hot air rising off hot ground, resulting in smaller disturbances such as dust devils, There are many varieties and names for storms, Ice storm — Ice storms are one of the most dangerous forms of winter storms. When surface temperatures are below freezing, but a layer of above-freezing air remains aloft, rain can fall into the freezing layer. In general,8 millimetres of accumulation is all that is required, especially in combination with breezy conditions, Ice storms also make unheated road surfaces too slick to drive upon. Ice storms can vary in range from hours to days and can cripple small towns. Blizzard — There are varying definitions for blizzards, both time and by location. In general, a blizzard is accompanied by winds, heavy snow. Snow storms, especially ones with a liquid equivalent and breezy conditions, can down tree limbs, cut off power. Ocean Storm — Storm conditions out at sea are defined as having sustained winds of 48 knots or greater, usually just referred to as a storm, these systems can sink vessels of all types and sizes. Firestorm — Firestorms are conflagrations which attain such intensity that they create and it is most commonly a natural phenomenon, created during some of the largest bushfires, forest fires, and wildfires. The Peshtigo Fire is one example of a firestorm, Firestorms can also be deliberate effects of targeted explosives such as occurred as a result of the aerial bombings of Dresden. Nuclear detonations generate firestorms if high winds are not present, dust devil — a small, localized updraft of rising air. Wind storm— A storm marked by high wind with little or no precipitation, windstorm damage often opens the door for massive amounts of water and debris to cause further damage to a structure. European windstorms and derechos are two type of windstorms, high wind is also the cause of sandstorms in dry climates. Squall — sudden onset of wind increase of at least 16 knots or greater sustained for at least one minute, gale — An extratropical storm with sustained winds between 34-48 knots. Thunderstorm — A thunderstorm is a type of storm that generates lightning and it is normally accompanied by heavy precipitation

31.
National Hurricane Center
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The Technology and Science Branch provides technical support for the center, which includes new infusions of technology from abroad. Research to improve operational forecasts is done through the Hurricane Forecast Improvement Project, during the Atlantic and northeast Pacific hurricane seasons, the Hurricane Specialists Unit issues routine tropical weather outlooks for the northeast Pacific and northern Atlantic oceans. When tropical storm or hurricane conditions are expected within 48 hours, the first hurricane warning service was set up in the 1870s from Cuba with the work of Father Benito Viñes. C. in 1902. The central office in Washington, which evolved into the National Meteorological Center and Weather Prediction Center, Hurricane advisories issued every six hours by the regional hurricane offices began at this time. The Jacksonville hurricane warning office moved to Miami, Florida in 1943, Tropical cyclone naming began for Atlantic tropical cyclones using the Joint Army/Navy Phonetic Alphabet by 1947. In 1950, the Miami Hurricane Warning Office began to prepare the annual hurricane season summary articles, in the 1953 Atlantic season, the United States Weather Bureau began naming storms which reach tropical storm intensity with human names. The National Hurricane Research Project, begun in the 1950s, used aircraft to study tropical cyclones, on July 1,1956, a National Hurricane Information Center was established in Miami, Florida which became a warehouse for all hurricane-related information from one United States Weather Bureau office. The Miami Hurricane Warning Office moved from Lindsey Hopkins Hotel to the Aviation Building 4 miles to the northwest on July 1,1958, the Miami HWO moved to the campus of the University of Miami in 1964, and was referred to as the NHC in 1965. The Miami HWO tropical cyclone reports were regularly and took on their modern format in 1964. Beginning in 1973, the National Meteorological Center duties gained advisory responsibility for tracking and publicizing inland tropical depressions, the World Meteorological Organization assumed control of the Atlantic hurricane naming list in 1977. In 1978, the NHCs offices moved off the campus of the University of Miami across U. S. Highway 1 to the IRE Financial Building, male names were added into the hurricane list beginning in the 1979 season. The hurricane warning offices remained active past 1983, in 1984, the NHC was separated from the Miami Weather Service Forecast Office, which meant the meteorologist in charge at Miami was no longer in a position above the hurricane center director. By 1988, the NHC gained responsibility for eastern Pacific tropical cyclones as the former Eastern Pacific Hurricane Center in San Francisco was decommissioned, in 1992, Hurricane Andrew blew the WSR-57 weather radar and the anemometer off the roof of NHCs/the Miami State Weather Forecast offices. The radar was replaced with a WSR-88D NEXRAD system in April 1993 installed near Metro Zoo, in 1995, the NHC moved into a new hurricane-resistant facility on the campus of Florida International University, capable of withstanding 130 mph winds. Its name was changed to the Tropical Prediction Center in 1995, after the name change to TPC, the Hurricane Specialists were grouped as a separate NHC unit under the Tropical Prediction Center, separating themselves from the Tropical Analysis and Forecast Branch. On October 1,2010, the Tropical Prediction Center was renamed the NHC, the World Meteorological Organization continues to create and maintain the annual hurricane naming lists. Naming lists use a rotation, with the deadliest or most notable storm names retired from the rotation. The director of the National Hurricane Center is Richard Knabb, for the fiscal year of 2008, the budget for the NHC was $6.8 million

32.
Nautical mile
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A nautical mile is a unit of measurement defined as exactly 1852 meters. Historically, it was defined as one minute of latitude, which is equivalent to one sixtieth of a degree of latitude. Today it is an SI derived unit, being rounded to a number of meters. The derived unit of speed is the knot, defined as one mile per hour. The geographical mile is the length of one minute of longitude along the Equator, there is no internationally agreed symbol. M is used as the abbreviation for the mile by the International Hydrographic Organization and by the International Bureau of Weights. NM is used by the International Civil Aviation Organization, nm is used by the U. S. National Oceanic and Atmospheric Administration. Nmi is used by the Institute of Electrical and Electronics Engineers, the word mile is from the Latin word for a thousand paces, mīlia. In 1617 the Dutch scientist Snell assessed the circumference of the Earth at 24,630 Roman miles, around that time British mathematician Edmund Gunter improved navigational tools including a new quadrant to determine latitude at sea. He reasoned that the lines of latitude could be used as the basis for a unit of measurement for distance, as one degree is 1/360 of a circle, one minute of arc is 1/21600 of a circle. These sexagesimal units originated in Babylonian astronomy, Gunter used Snells circumference to define a nautical mile as 6,080 feet, the length of one minute of arc at 48 degrees latitude.3 metres. Other countries measure the minute of arc at 45 degrees latitude, in 1929, the international nautical mile was defined by the First International Extraordinary Hydrographic Conference in Monaco as 1,852 meters. Imperial units and United States customary units used a definition of the nautical mile based on the Clarke Spheroid, the United States nautical mile was defined as 6,080.20 feet based in the Mendenhall Order foot of 1893. It was abandoned in favour of the nautical mile in 1954.181 meters. It was abandoned in 1970 and, legally, references to the unit are now converted to 1,853 meters. Conversion of units Orders of magnitude

33.
Eyewall replacement cycle
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Eyewall replacement cycles, also called concentric eyewall cycles, naturally occur in intense tropical cyclones, generally with winds greater than 185 km/h, or major hurricanes. Since the strongest winds are in a cyclones eyewall, the tropical cyclone usually weakens during this phase, eventually the outer eyewall replaces the inner one completely, and the storm may re-intensify. The discovery of this process was responsible for the end of the U. S. governments hurricane modification experiment Project Stormfury. This project set out to seed clouds outside the eyewall, apparently causing a new eyewall to form, when it was discovered that this was a natural process due to hurricane dynamics, the project was quickly abandoned. Almost every intense hurricane undergoes at least one of these cycles during its existence, recent studies have shown that nearly half of all tropical cyclones, and nearly all cyclones with sustained winds over 204 kilometres per hour, undergo eyewall replacement cycles. Hurricane Allen in 1980 went through repeated eyewall replacement cycles, fluctuating between Category 5 and Category 3 status on the Saffir-Simpson Hurricane Scale several times, Hurricane Juliette was a rare documented case of triple eyewalls. Typhoon June was the first reported case of triple eyewalls, the first tropical system to be observed with concentric eyewalls was Typhoon Sarah by Fortner in 1956, which he described as an eye within an eye. The storm was observed by an aircraft to have an inner eyewall at 6 kilometres. During a subsequent flight 8 hours later, the eyewall had disappeared, the outer eyewall had reduced to 16 kilometres. The next hurricane observed to have concentric eyewalls was Hurricane Donna in 1960, radar from reconnaissance aircraft showed an inner eye that varied from 10 miles at low altitude to 13 miles near the tropopause. In between the two eyewalls was an area of clear skies that extended vertically from 3,000 feet to 25,000 feet, the low-level clouds at around 3,000 feet were described as stratocumulus with concentric horizontal rolls. The inner eyewall was reported to heights near 45,000 feet while the inner eyewall only extended to 30,000 feet. 12 hours after identifying a concentric eyewalls, the eyewall had dissipated. Hurricane Beulah in 1967 was the first tropical cyclone to have its eyewall replacement cycle observed from beginning to end, previous observations of concentric eyewalls were from aircraft-based platforms. Beulah was observed from the Puerto Rico land-based radar for 34 hours during which time a double eyewall formed and dissipated and it was noted that Beulah reached maximum intensity immediately prior to undergoing the eyewall replacement cycle, and that it was probably more than a coincidence. Previous eyewall replacement cycles had been observed to decrease the intensity of the storm, the increased rate of precipitation would result in dissipation of the storm. By early 1960, the theory was that the eyewall of a hurricane was inertially unstable. Therefore, seeding the storm outside the eyewall would release more latent heat, the expansion of the eyewall would be accompanied with a decrease in the maximum wind speed through conservation of angular momentum

34.
Mathematical model
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A mathematical model is a description of a system using mathematical concepts and language. The process of developing a model is termed mathematical modeling. Mathematical models are used in the sciences and engineering disciplines. Physicists, engineers, statisticians, operations research analysts, and economists use mathematical models most extensively, a model may help to explain a system and to study the effects of different components, and to make predictions about behaviour. Mathematical models can take many forms, including systems, statistical models, differential equations. These and other types of models can overlap, with a model involving a variety of abstract structures. In general, mathematical models may include logical models, in many cases, the quality of a scientific field depends on how well the mathematical models developed on the theoretical side agree with results of repeatable experiments. Lack of agreement between theoretical mathematical models and experimental measurements often leads to important advances as better theories are developed, in the physical sciences, the traditional mathematical model contains four major elements. These are Governing equations Defining equations Constitutive equations Constraints Mathematical models are composed of relationships. Relationships can be described by operators, such as operators, functions, differential operators. Variables are abstractions of system parameters of interest, that can be quantified, a model is considered to be nonlinear otherwise. The definition of linearity and nonlinearity is dependent on context, for example, in a statistical linear model, it is assumed that a relationship is linear in the parameters, but it may be nonlinear in the predictor variables. Similarly, an equation is said to be linear if it can be written with linear differential operators. In a mathematical programming model, if the functions and constraints are represented entirely by linear equations. If one or more of the functions or constraints are represented with a nonlinear equation. Nonlinearity, even in simple systems, is often associated with phenomena such as chaos. Although there are exceptions, nonlinear systems and models tend to be difficult to study than linear ones. A common approach to nonlinear problems is linearization, but this can be if one is trying to study aspects such as irreversibility

35.
Thermodynamics
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Thermodynamics is a branch of science concerned with heat and temperature and their relation to energy and work. The behavior of these quantities is governed by the four laws of thermodynamics, the laws of thermodynamics are explained in terms of microscopic constituents by statistical mechanics. Thermodynamics applies to a variety of topics in science and engineering, especially physical chemistry, chemical engineering. The initial application of thermodynamics to mechanical heat engines was extended early on to the study of chemical compounds, Chemical thermodynamics studies the nature of the role of entropy in the process of chemical reactions and has provided the bulk of expansion and knowledge of the field. Other formulations of thermodynamics emerged in the following decades, statistical thermodynamics, or statistical mechanics, concerned itself with statistical predictions of the collective motion of particles from their microscopic behavior. In 1909, Constantin Carathéodory presented a mathematical approach to the field in his axiomatic formulation of thermodynamics. A description of any thermodynamic system employs the four laws of thermodynamics that form an axiomatic basis, the first law specifies that energy can be exchanged between physical systems as heat and work. In thermodynamics, interactions between large ensembles of objects are studied and categorized, central to this are the concepts of the thermodynamic system and its surroundings. A system is composed of particles, whose average motions define its properties, properties can be combined to express internal energy and thermodynamic potentials, which are useful for determining conditions for equilibrium and spontaneous processes. With these tools, thermodynamics can be used to describe how systems respond to changes in their environment and this can be applied to a wide variety of topics in science and engineering, such as engines, phase transitions, chemical reactions, transport phenomena, and even black holes. This article is focused mainly on classical thermodynamics which primarily studies systems in thermodynamic equilibrium, non-equilibrium thermodynamics is often treated as an extension of the classical treatment, but statistical mechanics has brought many advances to that field. Guericke was driven to make a vacuum in order to disprove Aristotles long-held supposition that nature abhors a vacuum. Shortly after Guericke, the English physicist and chemist Robert Boyle had learned of Guerickes designs and, in 1656, in coordination with English scientist Robert Hooke, using this pump, Boyle and Hooke noticed a correlation between pressure, temperature, and volume. In time, Boyles Law was formulated, which states that pressure, later designs implemented a steam release valve that kept the machine from exploding. By watching the valve rhythmically move up and down, Papin conceived of the idea of a piston and he did not, however, follow through with his design. Nevertheless, in 1697, based on Papins designs, engineer Thomas Savery built the first engine, although these early engines were crude and inefficient, they attracted the attention of the leading scientists of the time. Black and Watt performed experiments together, but it was Watt who conceived the idea of the condenser which resulted in a large increase in steam engine efficiency. Drawing on all the work led Sadi Carnot, the father of thermodynamics, to publish Reflections on the Motive Power of Fire

36.
Wind shear
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Wind shear, sometimes referred to as windshear or wind gradient, is a difference in wind speed and/or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as vertical or horizontal wind shear. Vertical wind shear is a change in speed or direction with change in altitude. Horizontal wind shear is a change in speed with change in lateral position for a given altitude. Wind shear has a significant effect during take-off and landing of aircraft due to its effects on control of the aircraft and this phenomenon is a concern for architects. Sound movement through the atmosphere is affected by shear, which can bend the wave front, causing sounds to be heard where they normally would not. The thermal wind concept explains how differences in speed at different heights are dependent on horizontal temperature differences. Wind shear refers to the variation of wind over either horizontal or vertical distances, airplane pilots generally regard significant wind shear to be a horizontal change in airspeed of 30 knots for light aircraft, and near 45 knots for airliners at flight altitude. Vertical speed changes greater than 4.9 knots also qualify as significant wind shear for aircraft, Low level wind shear can affect aircraft airspeed during take off and landing in disastrous ways, and airliner pilots are trained to avoid all microburst wind shear. Wind shear is also a key factor in the creation of severe thunderstorms, the additional hazard of turbulence is often associated with wind shear. Weather situations where shear is observed include, Weather fronts, significant shear is observed when the temperature difference across the front is 5 °C or more, and the front moves at 30 knots or faster. Because fronts are three-dimensional phenomena, frontal shear can be observed at any altitude between surface and tropopause, and therefore be seen both horizontally and vertically, vertical wind shear above warm fronts is more of an aviation concern than near and behind cold fronts due to their greater duration. Associated with upper level jet streams is a known as clear air turbulence. The CAT is strongest on the anticyclonic shear side of the jet, when a nocturnal low-level jet forms overnight above the Earths surface ahead of a cold front, significant low level vertical wind shear can develop near the lower portion of the low level jet. This is also known as wind shear since it is not due to nearby thunderstorms. When winds blow over a mountain, vertical shear is observed on the lee side, if the flow is strong enough, turbulent eddies known as rotors associated with lee waves may form, which are dangerous to ascending and descending aircraft. When on a clear and calm night, an inversion is formed near the ground. The change in wind can be 90 degrees in direction and 40 kt in speed, even a nocturnal low level jet can sometimes be observed

37.
United States
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Forty-eight of the fifty states and the federal district are contiguous and located in North America between Canada and Mexico. The state of Alaska is in the northwest corner of North America, bordered by Canada to the east, the state of Hawaii is an archipelago in the mid-Pacific Ocean. The U. S. territories are scattered about the Pacific Ocean, the geography, climate and wildlife of the country are extremely diverse. At 3.8 million square miles and with over 324 million people, the United States is the worlds third- or fourth-largest country by area, third-largest by land area. It is one of the worlds most ethnically diverse and multicultural nations, paleo-Indians migrated from Asia to the North American mainland at least 15,000 years ago. European colonization began in the 16th century, the United States emerged from 13 British colonies along the East Coast. Numerous disputes between Great Britain and the following the Seven Years War led to the American Revolution. On July 4,1776, during the course of the American Revolutionary War, the war ended in 1783 with recognition of the independence of the United States by Great Britain, representing the first successful war of independence against a European power. The current constitution was adopted in 1788, after the Articles of Confederation, the first ten amendments, collectively named the Bill of Rights, were ratified in 1791 and designed to guarantee many fundamental civil liberties. During the second half of the 19th century, the American Civil War led to the end of slavery in the country. By the end of century, the United States extended into the Pacific Ocean. The Spanish–American War and World War I confirmed the status as a global military power. The end of the Cold War and the dissolution of the Soviet Union in 1991 left the United States as the sole superpower. The U. S. is a member of the United Nations, World Bank, International Monetary Fund, Organization of American States. The United States is a developed country, with the worlds largest economy by nominal GDP. It ranks highly in several measures of performance, including average wage, human development, per capita GDP. While the U. S. economy is considered post-industrial, characterized by the dominance of services and knowledge economy, the United States is a prominent political and cultural force internationally, and a leader in scientific research and technological innovations. In 1507, the German cartographer Martin Waldseemüller produced a map on which he named the lands of the Western Hemisphere America after the Italian explorer and cartographer Amerigo Vespucci

38.
Flood
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A flood is an overflow of water that submerges land which is usually dry. The European Union Floods Directive defines a flood as a covering by water of land not normally covered by water, in the sense of flowing water, the word may also be applied to the inflow of the tide. Floods can also occur in rivers when the flow exceeds the capacity of the river channel. Floods often cause damage to homes and businesses if they are in the flood plains of rivers. Some floods develop slowly, while others such as floods, can develop in just a few minutes. Additionally, floods can be local, impacting a neighborhood or community, or very large, the word flood comes from the Old English flod, a word common to Germanic languages. Deluge myths are stories of a great flood sent by a deity or deities to destroy civilization as an act of divine retribution. Floods can happen on flat or low-lying areas when water is supplied by rainfall or snowmelt more rapidly than it can infiltrate or run off. The excess accumulates in place, sometimes to hazardous depths, surface soil can become saturated, which effectively stops infiltration, where the water table is shallow, such as a floodplain, or from intense rain from one or a series of storms. Infiltration also is slow to negligible through frozen ground, rock, concrete, paving, areal flooding begins in flat areas like floodplains and in local depressions not connected to a stream channel, because the velocity of overland flow depends on the surface slope. Endorheic basins may experience flooding during periods when precipitation exceeds evaporation. Floods occur in all types of river and stream channels, from the smallest ephemeral streams in humid zones to normally-dry channels in arid climates to the worlds largest rivers. When overland flow occurs on tilled fields, it can result in a flood where sediments are picked up by run off. Localized flooding may be caused or exacerbated by drainage obstructions such as landslides, ice, debris, slow-rising floods most commonly occur in large rivers with large catchment areas. The increase in flow may be the result of sustained rainfall, rapid snow melt, monsoons, the cause may be localized convective precipitation or sudden release from an upstream impoundment created behind a dam, landslide, or glacier. In one instance, a flood killed eight people enjoying the water on a Sunday afternoon at a popular waterfall in a narrow canyon. Without any observed rainfall, the rate increased from about 50 to 1,500 cubic feet per second in just one minute. Two larger floods occurred at the site within a week

Map of the cumulative tracks of all tropical cyclones during the 1985–2005 time period. The Pacific Ocean west of the International Date Line sees more tropical cyclones than any other basin, while there is almost no activity in the southern hemisphere between Africa and 160˚W.

Microburst schematic from NASA. Note the downward motion of the air until it hits ground level, then spreads outward in all directions. The wind regime in a microburst is completely opposite to a tornado.

Tropical cyclogenesis is the development and strengthening of a tropical cyclone in the atmosphere. The mechanisms …

Schematic representation of flow around a low-pressure area (in this case, Hurricane Isabel) in the Northern hemisphere. The pressure gradient force is represented by blue arrows, the Coriolis acceleration (always perpendicular to the velocity) by red arrows